The present invention relates to the field of waveguides for microwave signal transmission. Specifically, it pertains to waveguide configurations which, in cross section, have a ridge directly opposing a trough.
Typical hollow tubular waveguides are useful for transmitting microwave frequency signals. Unfortunately, such waveguides do not easily connect to coplanar waveguides. Furthermore, such waveguides may not have sufficient bandwidth.
Previously, ridge waveguides have been used when large bandwidth transmission capabilities are desired. Ridge waveguides also have been a convenient means of transforming the high impedance associated with waveguides to the relatively low impedance typically associated with dielectric-based transmission line structures, such as microstrip. Ridge waveguides generate a quasi-TEM field configuration which closely replicates the field configuration of microstrip transmission lines. Unfortunately, the ridge waveguide's quasi-TEM field configuration is very different from the field configuration of a coplanar waveguide's. Electrical connection between a ridge waveguide and a coplanar waveguide thus results in signal reflection and corresponding insertion loss.
What is needed, then, is a waveguide configuration which retains the broadband transmission capabilities of ridge waveguides yet provides a horizontal electric field configuration for efficient electrical connection to coplanar waveguides.